diff --git a/ipv4/helper.go b/ipv4/helper.go
index b494a2c..e845a73 100644
--- a/ipv4/helper.go
+++ b/ipv4/helper.go
@@ -13,16 +13,13 @@
 )
 
 var (
-	errInvalidConn              = errors.New("invalid connection")
-	errMissingAddress           = errors.New("missing address")
-	errMissingHeader            = errors.New("missing header")
-	errNilHeader                = errors.New("nil header")
-	errHeaderTooShort           = errors.New("header too short")
-	errExtHeaderTooShort        = errors.New("extension header too short")
-	errInvalidConnType          = errors.New("invalid conn type")
-	errNoSuchInterface          = errors.New("no such interface")
-	errNoSuchMulticastInterface = errors.New("no such multicast interface")
-	errNotImplemented           = errors.New("not implemented on " + runtime.GOOS + "/" + runtime.GOARCH)
+	errInvalidConn       = errors.New("invalid connection")
+	errMissingAddress    = errors.New("missing address")
+	errNilHeader         = errors.New("nil header")
+	errHeaderTooShort    = errors.New("header too short")
+	errExtHeaderTooShort = errors.New("extension header too short")
+	errInvalidConnType   = errors.New("invalid conn type")
+	errNotImplemented    = errors.New("not implemented on " + runtime.GOOS + "/" + runtime.GOARCH)
 
 	// See https://www.freebsd.org/doc/en/books/porters-handbook/versions.html.
 	freebsdVersion  uint32
diff --git a/ipv4/sys_asmreq.go b/ipv4/sys_asmreq.go
index c5eaafe..76d670a 100644
--- a/ipv4/sys_asmreq.go
+++ b/ipv4/sys_asmreq.go
@@ -7,12 +7,15 @@
 package ipv4
 
 import (
+	"errors"
 	"net"
 	"unsafe"
 
 	"golang.org/x/net/internal/socket"
 )
 
+var errNoSuchInterface = errors.New("no such interface")
+
 func (so *sockOpt) setIPMreq(c *socket.Conn, ifi *net.Interface, grp net.IP) error {
 	mreq := ipMreq{Multiaddr: [4]byte{grp[0], grp[1], grp[2], grp[3]}}
 	if err := setIPMreqInterface(&mreq, ifi); err != nil {
diff --git a/ipv6/helper.go b/ipv6/helper.go
index f767b1f..c2d508f 100644
--- a/ipv6/helper.go
+++ b/ipv6/helper.go
@@ -15,7 +15,6 @@
 	errMissingAddress  = errors.New("missing address")
 	errHeaderTooShort  = errors.New("header too short")
 	errInvalidConnType = errors.New("invalid conn type")
-	errNoSuchInterface = errors.New("no such interface")
 	errNotImplemented  = errors.New("not implemented on " + runtime.GOOS + "/" + runtime.GOARCH)
 )